Marshal, I have seen more than one 22LR wounds. They are scary to look at because they'll travel under the skin and then exit or ricochet of bone or whatever. I saw a fellow's wound from a 22 that hit him in the back above the hip and hit a rib. It must've ricocheted because it drove upward either stopping or exiting near his shoulder. Nasty looking - it looked similar to the OP's wound, as if it had sliced open the whole way or else the doctor did. Maybe it did. And that's not the only one.
I think if it was me in that outhouse, the first thing I'd of thought of was: "Where's my firearm?". It isn;t so much that it's an accident, rather it's that you don;t know it's innocent until the smoke clears, so to speak.
ON EDIT: And as Model 52 says, there're doctor's incisions weighed into the equation too.